In “They sat on the river bank,” what do the words “river” and “sat” do?

First Map of Legal Wording: Khas, Aam, Mushtarak and Mu'awwal

• They are a Qarinah that selects the side of a river rather than a financial bank
• They make both meanings of bank intended together
• They turn bank into a fixed number
• It proves the learner may perform independent Ijtihad